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Thermo Fisher Scientific

Environmental Instruments DivisionWater Analysis Instruments

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User GuideHigh Performance Ammonia Ion Selective Electrode

ROSS and the COIL trade dress are trademarks of Thermo Fisher Scientific Inc.

AQUAfast, Cahn, ionplus, KNIpHE, No Cal, ORION, perpHect, PerpHecT, PerpHecTion, pHISA, pHuture, Pure Water, Sage, Sensing the Future, SensorLink, ROSS, ROSS Ultra, Sure-Flow, Titrator PLUS and TURBO2 are registered trademarks of Thermo Fisher.

1-888-pHAX-ION, A+, All in One, Aplus, AQUAsnap, AssuredAccuracy, AUTO-BAR, AUTO-CAL, AUTO DISPENSER, Auto-ID, AUTO-LOG, AUTO-READ, AUTO-STIR, Auto-Test, BOD AutoEZ, Cable-Free, CERTI-CAL, CISA, DataCOLLECT, DataPLUS, digital LogR, DirectCal, DuraProbe, Environmental Product Authority, Extra Easy/Extra Value, FAST QC, GAP, GLPcal, GLPcheck, GLPdoc, ISEasy, KAP, LabConnect, LogR, Low Maintenance Triode, Minimum Stir Requirement, MSR, NISS, One-Touch, One-Touch Calibration, One-Touch Measurement, Optimum Results, Orion Star, Pentrode, pHuture MMS, pHuture Pentrode, pHuture Quatrode, pHuture Triode, Quatrode, QuiKcheK, rf link, ROSS Resolution, SAOB, SMART AVERAGING, Smart CheK, SMART STABILITY, Stacked, Star Navigator 21, Stat Face, The Enhanced Lab, ThermaSense, Triode, TRIUMpH, Unbreakable pH, Universal Access are trademarks of Thermo Fisher.

Guaranteed Success and The Technical Edge are service marks of Thermo Fisher.

PerpHecT meters are protected by U.S. patent 6,168,707.

PerpHecT ROSS are protected by U.S. patent 6,168,707.

ORION Series A meters and 900A printer are protected by U.S. patents 5,198,093, D334,208 and D346,753.

ionplus electrodes and Optimum Results solutions are protected by US Patent 5,830,338.

ROSS Ultra electrodes are protected by US patents 6,793,787.

Orion ORP Standard is protected by US Patent 6,350,367.

Orion NoCal electrodes with stabilized potential patent pending.

The specifications, descriptions, drawings, ordering information and part numbers within this document are subject to change without notice.

This publication supersedes all previous publications on this subject.

Table of Contents

General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Required .Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Electrode Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3Electrode .Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3Electrode .Preparation .with .Preassembled . .Outer .Body .and .Membrane .Cap .Assembly . . . . . . . . . . . . . . . . . .4Electrode .Preparation .with .Loose .Membrane . . . . . . . . . . . . . . . .6Checking .Electrode .Operation .(Slope) . . . . . . . . . . . . . . . . . . . . . .9Units .of .Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Sample .Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Measuring .Hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Sample .Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Electrode .Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Analytical Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . .13Typical .Calibration .Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Direct .Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Low-Level .Measurements .By .Direct .Calibration . . . . . . . . . . . . .20Measuring .Ammonia .in .Solutions .that .Wet .the .Membrane . . . .23Measuring .Organic .Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . .24Application .Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24Known .Addition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

Electrode Characteristics . . . . . . . . . . . . . . . . . . . . . . . . .31Electrode .Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31Temperature .Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32Interferences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32pH .Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33Complexation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33Effect .of .Dissolved .Species . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33Membrane .Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33Theory .of .Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37Troubleshooting .Checklist . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37Troubleshooting .Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40Assistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44

1High Performance Ammonia Electrode User Guide

General Information

IntroductionThe .high .performance .ammonia .ion .selective .electrode .(ISE) .allows .fast, .simple, .economical, .and .accurate .measurements .of .dissolved .ammonia .in .aqueous .solutions . . .This .gas .sensing .electrode .can .also .be .used .to .measure .the .ammonium .ion .after .conversion .to .ammonia .or .to .measure .organic .nitrogen .after .Kjeldahl .digestion .of .the .sample . . .Sample .color .and .turbidity .do .not .affect .the .measurement .and .samples .do .not .need .to .be .distilled . . .Almost .all .anions, .cations .and .dissolved .species, .other .than .volatile .amines, .do .not .interfere .

All .apparatus .and .solutions .required .for .measurement, .electrode .characteristics .and .electrode .theory .are .discussed .in .this .user .guide . . .General .analytical .procedures, .low-level .procedures .and .a .method .for .measuring .ammonia .in .solutions .that .wet .the .membrane .are .given .

The High Performance Ammonia Electrode Includes:

• . One .preassembled .outer .body .and .membrane .cap- .includes .outer .body, .membrane .cap .and .membrane

• . Twenty .loose .membranes

• . Tweezers .for .handling .loose .membranes

• . Electrode .filling .solution

• . Dispensing .cap .for .electrode .filling .solution

• . User .guide

There .are .two .measurement .techniques .that .are .recommended .for .direct .measurements .of .ammonia .samples . . .The .primary .direct .measurement .technique .is .for .ammonia .samples .with .concentrations .of .1 .ppm .ammonia .as .nitrogen .and .higher . . .The .low-level .measurement .technique .is .for .ammonia .samples .with .concentrations .of .1 .ppm .ammonia .as .nitrogen .and .lower . . .Refer .to .the .Analytical Techniques .section .for .details . . .

Technical .Support .Chemists .can .be .consulted .for .assistance .and .troubleshooting .advice . . .Within .the .United .States .call .1 .800 .225 .1480 .and .outside .the .United .States .call .978 .232 .6000 .or .fax .978 .232 .6031 . . .In .Europe, .the .Middle .East .and .Africa, .contact .your .local .authorized .dealer . . .For .the .most .current .contact .information, .visit .www .thermo .com/water .

� High Performance Ammonia Electrode User Guide

Required Equipment1 . . Thermo .Scientific .Orion .ISE .meter, .such .as .the .4-Star .pH/

ISE .meter .or .5-Star .pH/ISE/DO/conductivity .meter .

. Ammonia .electrodes .can .be .used .on .any .ISE .meter .with .a .BNC .or .U .S . .standard .connection . . .The .electrodes .can .also .be .used .on .meters .with .a .variety .of .inputs .when .an .adapter .cable .is .used . . .Visit .www .thermo .com/water .for .details .

2 . . Thermo .Scientific .Orion .high .performance .ammonia .ion .selective .electrode, .Cat . .No . .9512HPBNWP .or .9512HP01 . . .

3 . . Magnetic .stirrer .or .Orion .stirrer .probe, .Cat . .No . .096019 . . .The .Orion .stirrer .probe .can .be .used .with .3-Star, .4-Star .and .5-Star .benchtop .meters .

4 . . Volumetric .flasks, .graduated .cylinders .and .beakers . . .

5 . . Distilled .or .deionized .water . . .All .water .must .be .ammonia-free . . .Pass .distilled .or .deionized .water .through .an .ion-exchange .column .containing .a .strong .acidic .cation .exchange .resin, .such .as .Dowex .50W-X8 .

6 . . Ammonia .electrode .filling .solution, .Cat . .No . .951209 .

7 . . Ammonia .calibration .standards .

Cat. No. Description

951006 0 .1 .M .ammonia .chloride .standard

951007 1000 .ppm .ammonia .as .nitrogen .standard

951207 100 .ppm .ammonia .as .nitrogen .standard

8 . . Ionic .Strength .Adjuster .(ISA), .which .provides .a .constant .background .ionic .strength .and .adjusts .the .solution .pH .

951211 pH-adjusting .ISA, .for .samples .that .have .a .concentration .of .1 .ppm .as .nitrogen .or .higher

951011 Alkaline .reagent .(low-level .ISA), .for .samples .that .have .a .concentration .of .1 .ppm .as .nitrogen .or .lower

9 . . Ammonia .electrode .storage .solution, .100 .mL .of .1 .ppm .standard .with .1 .mL .of .alkaline .reagent .(Cat . .No . .951011) . . .Refer .to .the .Electrode Storage .section .for .detailed .instructions .on .storage .solution .preparation . .

Electrode Setup

Electrode Assembly

Note: A new electrode is shipped without a membrane. You must install a preassembled outer body and membrane cap assembly or a new membrane before using the electrode.

Note: A new electrode is shipped dry. You must soak the inner body of the electrode in the electrode filling solution for at least two hours before using the electrode. For best results, soak the inner body overnight in electrode filling solution.

Assemble .the .electrode .according .to .the .instructions .listed .in .the .Electrode Preparation with a Preassembled Outer Body and Membrane Cap Assembly .or .Electrode Preparation with Loose Membranes section . . .Avoid .excessive .handling .of .the .membrane .during .assembly; .this .may .affect .the .hydrophobic .properties .of .the .membrane .and .cause .a .shortened .membrane .life . . .Use .the .tweezers .provided . . .A .membrane .will .last .from .one .week .to .several .months, .depending .on .usage . .

4 High Performance Ammonia Electrode User Guide

Electrode Preparation with a Preassembled Outer Body and Membrane Cap Assembly1 . . . Hold .the .electrode .vertically .and .unscrew .the .electrode .cap .

from .the .electrode .body . . .See .Figure 1 .

2 . . Carefully .remove .the .inner .body .from .the .outer .body .assembly . . .See Figure 2 . . .Dispose .of .any .electrode .filling .solution .that .is .in .the .outer .body .

fill fill fill

Figure 1 Figure 2 Figure 3

�High Performance Ammonia Electrode User Guide

3 . . . Select .a .new .preassembled .outer .body .and .membrane .cap .assembly .and .verify .that .the .membrane .is .not .wrinkled .or .torn . . .See .Figure 3 .

4 . . Fill .the .preassembled .outer .body .and .membrane .cap .to .the .fill .line .with .electrode .filling .solution . . .See .Figure 4 .

5 . . Insert .the .inner .body .into .the .preassembled .outer .body .and .membrane .cap . . .Ensure .that .the .inner .body .is .fully .inserted .in .the .top .of .the .outer .body .and .then .screw .on .the .electrode .cap . .See .Figure 5 .

6 . . Gently .tap .the .side .of .the .electrode .to .remove .air .bubbles .

7 . . Soak .the .electrode .in .the .ammonia .electrode .storage .solution .for .at .least .15 .minutes .before .use . . .Prepare .the .storage .solution .by .combining .100 .mL .of .1 .ppm .ammonia .standard .with .1 .mL .of .alkaline .reagent, .Cat . .No . .951011 .

filling

solutio

Figure 4 Figure 5

Electrode Preparation with Loose Membrane1 . . . Hold .the .electrode .vertically .and .unscrew .the .electrode .cap .

from .the .electrode .body . . .See .Figure 6 .

2 . . Carefully .remove .the .inner .body .from .the .outer .body .assembly . . .See .Figure 7 . . .Dispose .of .any .electrode .filling .solution .that .is .in .the .outer .body .

3 . . . Unscrew .the .membrane .cap .from .the .outer .body . . .See .Figure 8 . . .Remove .the .membrane .from .the .membrane .cap .if .a .membrane .was .previously .installed .

fill fill

4 . . Wear .gloves .and .use .tweezers .to .carefully .grasp .the .corner .of .the .white .membrane .from .between .wax .paper .separators . . .See .Figure 9 .

Note: Do not touch the center of the membrane.

5 . . Hold .the .outer .body .oriented .with .the .smaller .diameter .threads .at .the .top . . .See .Figure 10 . . .

6 . . Align .the .serrated .edge .of .the .membrane .against .the .threaded .shoulder .and .hold .the .membrane .with .your .thumb . . .See .Figure 11 . . .

7 . . With .the .other .hand, .gently .place .the .membrane .across .the .opening . . .See .Figure 12 .

8 . . Then .place .the .membrane .down .to .align .the .other .edge .with .the .opposite .shoulder . . .See .Figure 13 . . .

9 . . While .holding .each .edge .on .both .sides, .gently .place .each .smooth .side .of .the .membrane .out .and .down .over .the .threads .and .ensure .that .the .membrane .surface .is .smooth .and .without .wrinkles . . .See .Figure 14 . . .

10 . . Smooth .any .loose .material, .taking .care .not .to .touch .center .of .membrane . . .See .Figure 15 .

Figure 12 Figure 13 Figure 14 Figure 15

Note: Do not stretch the membrane.

11 . . . Screw .the .membrane .cap .onto .the .outer .body, .being .careful .not .to .touch .membrane . . .See .Figure 16. . .Screw .the .membrane .cap .on .half .way .and .wrap .any .loose .membrane .material .onto .the .threads .and .under .the .cap . .Make .sure .the .cap .is .fully .screwed .on .

12 . . Fill .the .outer .body .to .the .fill .line .with .electrode .filling .solution . . .See .Figure 17 .

13 . . Insert .the .inner .body .into .the .outer .body . . .Ensure .that .the .inner .body .is .fully .inserted .in .the .top .of .the .outer .body .and .then .screw .on .the .electrode .cap . . .See .Figure 18 .

14 . . Gently .tap .the .side .of .the .electrode .to .remove .air .bubbles . .

15 . . Soak .the .electrode .in .the .ammonia .electrode .storage .solution .for .at .least .15 .minutes .before .use . . .Prepare .the .storage .solution .by .combining .100 .mL .of .1 .ppm .ammonia .standard .with .1 .mL .of .alkaline .reagent, .Cat . .No . .951011 . .

filling

solutio

�High Performance Ammonia Electrode User Guide

Checking Electrode Operation (Slope)This .procedure .measures .electrode .slope . . .Slope .is .defined .as .the .change .in .millivolts .observed .with .every .tenfold .change .in .concentration . . .Obtaining .the .slope .value .provides .the .best .means .for .checking .electrode .operation . . .These .are .general .instructions .that .can .be .used .with .most .meters .to .check .the .electrode .operation . . .See .the .meter .user .guide .for .more .specific .information . .

1 . . If .the .electrode .has .been .stored .dry, .prepare .the .electrode .as .described .in .the .Electrode Preparation section .

2 . . Connect .the .electrode .to .the .meter . . .

3 . . Place .100 .mL .of .distilled .water .into .a .150 .mL .beaker . . .Add .2 .mL .of .pH-adjusting .ISA, .Cat . .No . .951211 . . .Stir .the .solution .thoroughly . . .Set .the .meter .to .the .mV .mode .

4 . . Rinse .the .electrode .by .immersing .it .in .distilled .water, .blot .it .dry .and .place .it .into .the .solution .prepared .in .step .3 . . .To .prevent .air .entrapment .on .the .membrane .surface, .be .sure .to .use .an .electrode .holder .that .keeps .the .electrode .at .a .20˚ .angle . . .If .air .bubbles .appear .on .the .sensing .membrane, .gently .tap .the .electrode .to .remove .the .bubbles .

5 . . Select .either .a .0 .1 .M .ammonium .chloride .or .1000 .ppm .ammonia .as .nitrogen .standard . . .Pipette .1 .mL .of .the .standard .into .the .beaker .and .stir .the .solution .thoroughly . . .When .a .stable .reading .is .displayed, .record .the .electrode .potential .in .millivolts .

6 . . Pipette .10 .mL .of .the .same .standard .into .the .same .beaker . . .Stir .the .solution .thoroughly . . .When .a .stable .reading .is .displayed, .record .the .electrode .potential .in .millivolts .

7 . . . There .should .be .a .54 .to .60 .mV .difference .between .the .two .millivolt .readings .when .the .solution .temperature .is .between .20-25 .˚C . . .If .the .millivolt .potential .is .not .within .this .range, .refer .to .the .Troubleshooting .section .

Note: If working with ammonia samples with concentrations of 1 ppm as nitrogen and lower, refer to the Low-Level Measurements by Direct Calibration section for a low-level checking electrode operation procedure.

Units of MeasurementAmmonia .can .be .measured .in .units .of .moles .per .liter .(M), .parts .per .million .as .ammonia, .parts .per .million .as .nitrogen .or .any .other .convenient .unit . . .See .Table 1 .

Table 1Concentration Unit Conversion Factors

moles/liter (M) ppm as nitrogen (N) ppm as ammonia (NH3)

10-4 1.40 1.70

10-3 14.0 17.0

10-2 140 170

10-1 1400 1700

Sample RequirementsSamples .must .be .aqueous; .they .must .not .contain .organic .solvents . . .Contact .Technical .Support .for .recommendations .on .the .use .of .the .electrode .in .unusual .applications . . .Samples .and .standards .should .be .at .the .same .temperature . . .A .1 .˚C .difference .in .temperature .will .give .rise .to .about .2% .measurement .error . . .In .all .analytical .procedures, .ISA .must .be .added .to .all .samples .and .standards .immediately .before .measurement . . .After .addition .of .the .ISA, .all .solutions .should .fall .within .a .pH .11 .to .14 .range .(solutions .should .be .blue .in .this .range .when .using .the .pH-adjusting .ISA, .Cat . .No . .951211) .and .have .a .total .level .of .dissolved .species .below .1 .M . . .If .the .total .level .of .dissolved .species .is .above .1 .M, .see .the .Effect of Dissolved Species .section . .

Measuring Hints• . Store .samples .according .to .the .Sample Storage .section .

• . Use .beakers .that .minimize .the .ratio .of .surface .area .to .volume .

• . Keep .beakers .containing .standards .and .samples .covered .between .measurements .

• . If .working .with .samples .that .have .a .concentration .of .1 .ppm .as .nitrogen .or .higher, .add .2 .mL .of .pH-adjusting .ISA .(Cat . .No . .951211) .to .every .100 .mL .of .sample .or .standard . . .Once .the .ISA .is .added, .a .blue .color .should .be .observed . . .

• . For .samples .that .have .a .concentration .of .1 .ppm .as .nitrogen .or .lower, .add .1 .mL .of .alkaline .reagent .(Cat . .No . .951011) .to .every .100 .mL .of .standard .or .sample . . .

• . ISA .should .be .added .immediately .before .a .measurement .is .made .to .prevent .ammonia .loss . .

• . Between .measurements, .rinse .the .electrode .by .immersing .it .in .distilled .water .

• . Be .sure .samples, .standards .and .the .electrode .are .at .the .same .temperature .

• . Samples .and .standards .should .be .stirred .using .a .magnetic .stirrer .or .stirrer .probe . . .Some .magnetic .stirrers .generate .enough .heat .to .change .solution .temperature . . .Place .a .piece .of .insulating .material .such .as .cork .or .styrofoam .between .the .beaker .and .the .stirring .plate .to .minimize .this .effect .

• . Stir .all .standards .and .samples .at .a .moderate, .uniform .rate . .

• . Verify .calibration .every .two .hours .by .placing .the .electrode .in .a .fresh .aliquot .of .the .middle .or .high .concentration .standard .used .for .calibration . . .If .the .value .has .changed, .recalibrate .the .electrode .

• . Always .use .fresh .standards .for .calibration .

• . After .immersion .in .solution, .check .the .electrode .for .any .air .bubbles .on .the .membrane .surface .and .remove .bubbles .by .gently .tapping .the .electrode .

• . If .electrode .response .is .slow, .replace .the .membrane .and .soak .the .electrode .for .at .least .15 .minutes .in .the .ammonia .electrode .storage .solution . . .Refer .to .the .Electrode Preparation .section .

1� High Performance Ammonia Electrode User Guide

Sample StorageIf .possible, .alkaline .samples .should .be .measured .immediately . . .The .rate .of .ammonia .loss .at .room .temperature .from .a .stirred .100 .mL .basic .solution .in .a .100 .mL .beaker .is .about .50% .in .six .hours . . .If .samples .must .be .stored, .make .them .slightly .acidic .(pH .6) .by .adding .0 .5 .mL .of .1 .M .HCl .to .each .liter .of .sample, .and .place .samples .in .tightly .capped .vessels . . .Make .stored .samples .basic .by .adding .ISA .immediately .before .measurement .

For .information .on .EPA .regulations .on .ammonia .sample .storage, .visit .the .Applications .and .Technical .Resources .section .of .our .website .at .www .thermo .com/water .

Electrode Storage

Note: The membrane must not be allowed to dry out. If the membrane is left out of solution, replace the membrane. Refer to the Electrode Preparation section.

Storage between measurements– Store .the .electrode .in .the .ammonia .electrode .storage .solution . . .Prepare .the .storage .solution .by .combining .100 .mL .of .1 .ppm .standard .with .1 .mL .of .alkaline .reagent .(Cat . .No . .951011) . .

To .make .the .storage .solution .using .the .0 .1 .M .ammonia .chloride .standard, .pipette .0 .07 .mL .of .the .standard .and .1 .mL .of .the .alkaline .reagent .into .a .100 .mL .volumetric .flask .and .dilute .to .the .mark .on .the .flask .with .distilled .water .

To .make .the .storage .solution .using .the .1000 .ppm .ammonia .as .nitrogen .standard, .pipette .0 .1 .mL .of .the .standard .and .1 .mL .of .the .alkaline .reagent .into .a .100 .mL .volumetric .flask .and .dilute .to .the .mark .on .the .flask .with .distilled .water .

To .make .the .storage .solution .using .the .100 .ppm .ammonia .as .nitrogen .standard, .pipette .1 .mL .of .the .standard .and .1 .mL .of .the .alkaline .reagent .into .a .100 .mL .volumetric .flask .and .dilute .to .the .mark .on .the .flask .with .distilled .water .

Overnight storage and storage up to one week– Store .the .electrode .in .the .electrode .filling .solution, .Cat . .No . .951209 .

Storage over one week– Disassemble .the .electrode .and .rinse .all .the .components .with .distilled .water . . .Dry .and .reassemble .the .electrode .without .electrode .filling .solution .and .without .a .membrane . . .When .preparing .the .electrode .for .use, .follow .the .procedures .in .the .Electrode Preparation .section . .

Analytical TechniquesA .variety .of .analytical .techniques .are .available .to .the .analyst . . .The .following .is .a .description .of .these .techniques .

Direct Calibration .is .a .simple .procedure .for .measuring .a .large .number .of .samples . . .Only .one .meter .reading .is .required .for .each .sample . . .Calibration .is .performed .using .a .series .of .standards . . .The .concentration .of .the .samples .is .determined .by .comparison .to .the .standards . . .ISA .is .added .to .all .solutions .to .ensure .that .samples .and .standards .have .similar .ionic .strength . .

Incremental Techniques .provide .a .useful .method .for .measuring .samples, .since .calibration .is .not .required . . .As .in .direct .calibration, .any .convenient .concentration .unit .can .be .used . . .The .different .incremental .techniques .are .described .below . . .They .can .be .used .to .measure .the .total .concentration .of .a .specific .ion .in .the .presence .of .a .large .(50-100 .times) .excess .of .complexing .agents .

• . Known Addition .is .useful .for .measuring .dilute .samples, .checking .the .results .of .direct .calibration .(when .no .complexing .agents .are .present), .or .measuring .the .total .concentration .of .an .ion .in .the .presence .of .an .excess .complexing .agent . . .The .electrode .is .immersed .in .the .sample .solution .and .an .aliquot .of .a .standard .solution .containing .the .measured .species .is .added .to .the .sample . . .From .the .change .in .potential .before .and .after .the .addition, .the .original .sample .concentration .is .determined .

• . Known Subtraction .is .useful .as .a .quick .version .of .a .titration, .or .for .measuring .species .for .which .stable .standards .do .not .exist . . .It .is .necessary .to .know .the .stoichiometric .ratio .between .standard .and .sample . . .For .known .subtraction, .an .electrode .sensing .the .sample .species .is .used . . .Stable .standards .of .a .species .reacting .completely .with .the .sample .in .a .reaction .of .known .stoichiometry .are .necessary .

• . Analate Addition .is .often .used .to .measure .soluble .solid .samples, .viscous .samples, .small .or .very .concentrated .samples, .to .diminish .the .effects .of .complex .sample .matrices, .or .to .diminish .the .effects .of .varying .sample .temperatures . . .This .method .is .not .suitable .for .dilute .or .low .concentration .samples . . .Total .concentration .is .measured .even .in .the .presence .of .complexing .agents . . .The .electrode .is .immersed .in .a .standard .solution .containing .the .ion .to .be .measured .and .an .aliquot .of .the .sample .is .added .to .the .standard . . .The .original .sample .concentration .is .determined .from .the .change .in .potential .before .and .after .the .addition .

• . Analate Subtraction .is .used .in .the .measurement .of .ions .for .which .no .ion-selective .electrode .exists . . .The .electrode .is .immersed .in .a .reagent .solution .that .contains .a .species .that .the .electrode .senses, .and .that .reacts .with .the .sample . . .It .is .useful .when .sample .size .is .small, .or .samples .for .which .a .stable .standard .is .difficult .to .prepare, .and .for .viscous .or .very .concentrated .samples . . .The .method .is .not .suited .for .very .dilute .samples . . .It .is .also .necessary .to .know .the .stoichiometric .ratio .between .standard .and .sample . . .

.• . Titrations .are .quantitative .analytical .techniques .for .measuring .the .concentration .of .a .species .by .incremental .addition .of .a .reagent .(titrant) .that .reacts .with .the .sample .species . . .Sensing .electrodes .can .be .used .for .determination .of .the .titration .end .point . . .Ion .selective .electrodes .are .useful .as .end .point .detectors, .because .they .are .unaffected .by .sample .color .or .turbidity . . .Titrations .are .approximately .10 .times .more .precise .than .direct .calibration, .but .are .more .time-consuming .

1�High Performance Ammonia Electrode User Guide

Typical Calibration CurveIn .the .direct .calibration .procedure, .a .calibration .curve .is .constructed .either .in .the .meter .memory .or .on .semi-logarithmic .paper . . .Electrode .potentials .of .standard .solutions .are .measured .and .plotted .on .the .linear .axis .against .their .concentrations .on . .the .log .axis . . .In .the .linear .regions .of .the .curves, .only .two .standards .are .needed .to .determine .a .calibration .curve . . .In .non-linear .regions, .more .points .must .be .taken . . .Procedures .are .given .in .the .Direct Calibration .section .for .concentrations .in .the .linear .region .of .electrode .response . . .The .Low-Level Measurements By Direct Calibration .section .provides .procedures .for .measurements .in .the .non-linear .region .of .electrode .response .

Figure 19: Typical Ammonia Electrode Calibration Curve

25010-4 10-3 10-2 10-1 0 10 102 103 104

Log NH3-N Concentration (mg/L)

Direct Calibration Setup

1 . . . Prepare .the .electrode .as .described .in .the .Electrode Preparation .section .

2 . . . Connect .the .electrode .to .the .meter .

3 . . . Prepare .at .least .two .standards .that .bracket .the .expected .sample .range .and .differ .in .concentration .by .a .factor .of .ten . . .Standards .can .be .prepared .in .any .concentration .unit .to .suit .the .particular .analysis .requirement . . .All .standards .should .be .at .the .same .temperature .as .the .samples . . .For .details .on .temperature .effects .on .electrode .performance, .refer .to .the .Temperature Effects section .

Serial Dilutions

Serial .dilution .is .the .best .method .for .the .preparation .of .standards . . .Serial .dilution .means .that .an .initial .standard .is .diluted, .using .volumetric .glassware, .to .prepare .a .second .standard .solution . . .The .second .standard .is .similarly .diluted .to .prepare .a .third .standard, .and .so .on, .until .the .desired .range .of .standards .has .been .prepared . .

1 . . . To prepare a 10-2 M NH4Cl standard (170 ppm as NH3 and 140 ppm as N)– .Pipette .10 .mL .of .the .0 .1 .M .NH4Cl .standard .into .a .100 .mL .volumetric .flask . .Dilute .to .mark .with .deionized .water .and .mix .well .

2 . . . To prepare a 10-3 M NH4Cl standard (17 ppm as NH3 and 14 ppm as N)– .Pipette .10 .mL .of .the .10-2 .M .NH4Cl .standard .into .a .100 .mL .volumetric .flask . .Dilute .to .mark .with .deionized .water .and .mix .well .

3 . . . To prepare a 10-4 M NH4Cl standard (1.7 ppm as NH3 and 1.4 ppm as N)– .Pipette .10 .mL .of .the .10-3 .M .NH4Cl .standard .into .a .100 .mL .volumetric .flask . .Dilute .to .mark .with .deionized .water .and .mix .well .

4 . . . To prepare a 10-5 M NH4Cl standard (0.17 ppm as NH3 and 0.14 ppm as N)– .Pipette .10 .mL .of .the .10-4 .M .NH4Cl .standard .into .a .100 .mL .volumetric .flask . .Dilute .to .mark .with .deionized .water .and .mix .well .

To .prepare .standards .with .a .different .concentration .use .the .following .formula:

C1 * V1 = C2 * V2

. C1 .= .concentration .of .original .standard

. V1 .= .volume .of .original .standard

. C2 .= .concentration .of .standard .after .dilution

. V2 .= .volume .of .standard .after .dilution

For .example, .to .prepare .100 .mL .of .25 .ppm .as .NH3 .standard .from .a .500 .ppm .as .NH3 .standard:

. C1 .= .500 .ppm .as .NH3

. V1 .= .unknown

. C2 .= .25 .ppm .as .NH3

. V2 .= .100 .mL

. 500 .ppm .* .V1 .= .25 .ppm .* .100 .mL

. V1 .= .(25 .ppm .* .100 .mL) ./ .500 .ppm .= .5 .mL

To .make .the .25 .ppm .as .NH3 .standard: .Pipette .5 .mL .of .the . .500 .ppm .as .NH3 .standard .into .a .100 .mL .volumetric .flask . . .Dilute .to .mark .with .deionized .water .and .mix .well . .

Direct Calibration Using a Meter with an ISE (Concentration) Mode

Note: See the meter user guide for more specific information.

1 . . Measure .100 .mL .of .the .less .concentrated .standard .into .a .150 .mL .beaker . . .Add .2 .mL .of .pH-adjusting .ISA . . .Stir .the .solution .thoroughly .

2 . . Rinse .the .electrode .by .immersing .it .in .distilled .water, .blot .it .dry .and .place .it .into .the .beaker .with .the .less .concentrated .standard . . .Wait .for .a .stable .reading .and .then .adjust .the .meter .to .display .the .value .of .the .standard, .as .described .in .the .meter .user .guide .

3 . . Measure .100 .mL .of .the .more .concentrated .standard .into .a .second .150 .mL .beaker . . .Add .2 .mL .of .pH-adjusting .ISA . . .Stir .the .solution .thoroughly .

4 . . Rinse .the .electrode .by .immersing .it .in .distilled .water, .blot .it .dry .and .place .it .into .the .beaker .with .the .more .concentrated .standard . . .Wait .for .a .stable .reading .and .then .adjust .the .meter .to .display .the .value .of .the .second .standard, .as .described .in .the .meter .user .guide .

5 . . Record .the .resulting .slope .value . . .The .slope .should .be .between .-54 .to .-60 .mV .when .the .standards .are .between . .20-25 .˚C . .

6 . . Measure .100 .mL .of .the .sample .into .a .150 .mL .beaker . . .Add .2 .mL .of .pH-adjusting .ISA . . .Stir .the .solution .thoroughly .

7 . . Rinse .the .electrode .by .immersing .it .in .distilled .water, .blot .it .dry .and .place .it .into .sample . . .The .concentration .will .be .displayed .on .the .meter . .

Note: Smaller volumes of solutions may be used as long as the ratio of standard or sample to pH-adjusting ISA does not change. For example, 50 mL of standard or sample requires the addition of 1 mL of pH-adjusting ISA.

Direct Calibration Using a Meter with a Millivolt Mode

1 . . Adjust .the .meter .to .measure .mV .

2 . . Measure .100 .mL .of .the .less .concentrated .standard .into .a .150 .mL .beaker . . .Add .2 .mL .of .pH-adjusting .ISA . . .Stir .the .solution .thoroughly .

3 . . Rinse .the .electrode .by .immersing .it .in .distilled .water, .blot .it .dry .and .place .it .into .the .beaker .with .the .less .concentrated .standard . . .When .a .stable .reading .is .displayed, .record .the .mV .value .and .corresponding .standard .concentration .

4 . . Measure .100 .mL .of .the .more .concentrated .standard .into .a .second .150 .mL .beaker . . .Add .2 .mL .of .pH-adjusting .ISA . . .Stir .the .solution .thoroughly .

5 . . Rinse .the .electrode .by .immersing .it .in .distilled .water, .blot .it .dry .and .place .it .into .the .beaker .with .the .more .concentrated .standard . . .When .a .stable .reading .is .displayed, .record .the .mV .value .and .corresponding .standard .concentration .

6 . . Using .semi-logarithmic .graph .paper .or .a .spreadsheet, .prepare .a .calibration .curve .by .plotting .the .millivolt .values .on .the .linear .axis .and .the .standard .concentration .values .on .the .logarithmic .axis .

7 . . Measure .100 .mL .of .the .sample .into .a .150 .mL .beaker . . . .Add .2 .mL .of .pH-adjusting .ISA . . .Stir .the .solution .thoroughly .

8 . . Rinse .the .electrode .by .immersing .it .in .distilled .water, .blot .it .dry .and .place .it .into .the .sample . . .When .a .stable .reading .is .displayed, .record .the .mV .value .

9 . . Using .the .calibration .curve .prepared .in .step .6, .determine .the .unknown .concentration .of .the .sample .

�0 High Performance Ammonia Electrode User Guide

Low-Level Measurements By Direct CalibrationThese .procedures .are .for .solutions .with .a .concentration .of . .1 .ppm .ammonia .as .nitrogen .(7 .x .10-5 .M, .1 .2 .ppm .as .ammonia) .or .less . . .For .solutions .low .in .ammonia .but .high .in .total .ionic .strength, .perform .the .same .procedure .with .one .change: .prepare .a .calibration .solution .with .a .background .composition .similar .to .the .sample . . .Accurate .measurement .requires .that .the .following .conditions .be .met:

• . . Adequate .time .must .be .allowed .for .electrode .stabilization . .Longer .response .time .will .be .needed .for .low-level .measurements

• . . Remember .to .stir .all .standards .and .samples .at .a .moderate, .uniform .rate

Electrode .response .is .relatively .slow .at .low .levels .of .ammonia .and .is .faster .going .in .the .direction .of .increasing .concentration . . . . .When .measuring .low .levels .of .ammonia, .keep .samples .and .standards .covered .and .work .with .large .solution .volumes .to .minimize .surface-area-to-volume .ratio . . .This .avoids .ammonia .absorption .from .air . . .Time .response .is .slow .at .ammonia .concentrations .of .0 .1 .ppm .ammonia .as .nitrogen .and .lower . . .Allow .up .to .5 .minutes .for .a .stable .reading .in .a .low-level .standard .or .sample .

1 . . . Prepare .the .electrode .as .described .in .the .Electrode Preparation .section . . .

2 . . . Soak .the .electrode .in .ammonia .electrode .storage .solution .for .at .least .15 .minutes . . .

3 . . Rinse .the .electrode .by .immersing .it .in .distilled .water .and .then .blot .it .dry . . .

4 . . . Connect .the .electrode .to .the .meter .

�1High Performance Ammonia Electrode User Guide

Low-Level Checking Electrode Operation (Slope)

This .procedure .measures .electrode .slope . . .Slope .is .defined .as .the .change .in .millivolts .observed .with .every .tenfold .change .in .concentration . . .Obtaining .the .slope .value .provides .the .best .means .for .checking .electrode .operation . . .These .are .general .instructions .that .can .be .used .with .most .meters .to .check .the .electrode .operation . . .See .the .meter .user .guide .for .more .specific .information . .

1 . . Place .100 .mL .of .distilled .water .into .a .150 .mL .beaker . . .Add .1 .mL .of .alkaline .reagent, .Cat . .No . .951011 . . .Stir .the .solution .thoroughly . . .Set .the .meter .to .the .mV .mode .

2 . . Rinse .the .electrode .by .immersing .it .in .distilled .water, .blot .it .dry .and .place .it .into .the .solution .prepared .in .step .1 . . .To .prevent .air .entrapment .on .the .membrane .surface, .be .sure .to .use .an .electrode .holder .that .keeps .the .electrode .at .a .20˚ .angle . . .If .air .bubbles .appear .on .the .sensing .membrane, .gently .tap .the .electrode .to .remove .the .bubbles .

3 . . Select .either .a .100 .ppm .ammonia .as .nitrogen .standard .or .10 .ppm .ammonia .as .nitrogen .standard . . .Pipette .1 .mL .of .the .standard .into .the .beaker .and .stir .the .solution .thoroughly . . .When .a .stable .reading .is .displayed, .record .the .electrode .potential .in .millivolts .

4 . . Pipette .10 .mL .of .the .same .standard .into .the .same .beaker . . .Stir .the .solution .thoroughly . . .When .a .stable .reading .is .displayed, .record .the .electrode .potential .in .millivolts .

5 . . . There .should .be .a .54 .to .60 .mV .difference .between .the .two .millivolt .readings .when .the .solution .temperature .is .between .20-25 .˚C . . .If .the .millivolt .potential .is .not .within .this .range, .refer .to .the .Troubleshooting .section .

�� High Performance Ammonia Electrode User Guide

Low-Level Calibration

1 . . Prepare .a .1 .ppm .ammonia .as .nitrogen .standard .by .pipetting .10 .mL .of .the .100 .ppm .ammonia .as .nitrogen .standard .into .a .1 .L .volumetric .flask .and .diluting .to .the .mark .with .deionized .water .

2 . . Prepare .a .0 .1 .ppm .ammonia .as .nitrogen .standard .by .pipetting .50 .mL .of .the .1 .ppm .ammonia .as .nitrogen .standard .into .a .500 .mL .volumetric .flask .and .diluting .to .the .mark .with .deionized .water . .

3 . . Prepare .a .0 .01 .ppm .ammonia .as .nitrogen .standard .by .pipetting .50 .mL .of .the .0 .1 .ppm .ammonia .as .nitrogen .standard .into .a .500 .mL .volumetric .flask .and .diluting .to .the .mark .with .deionized .water . .

4 . . Measure .50 .mL .of .each .standard .and .pour .the .standards .into .separate, .clean .beakers . . .Just .prior .to .calibration, .add .0 .5 .mL .of .alkaline .reagent, .Cat . .No . .951011, .to .each .beaker .

5 . . Set .the .meter .measurement .mode .to .ISE . . .If .using .a .Thermo .Scientific .Orion .Star .Series .meter .or .equivalent .meter, .set .the .stirrer .speed .to .4 .and .the .read .type .to .continuous . . .In .the .ISE .setup .mode, .set .the .resolution .to .3, .the .units .to .mg/L, .the .range .to .low .and .turn .on .the .blank .correction .feature . .

6 . . Perform .a .three .point .calibration .using .the .0 .01 .ppm .ammonia .as .nitrogen, .0 .1 .ppm .ammonia .as .nitrogen . .and .1 .ppm .ammonia .as .nitrogen .standards . . .Between .standards, .rinse .the .electrode .by .immersing .it .in .distilled .water .and .then .blot .it .dry . . .Stir .all .solutions .throughout .the .procedure . . .Calibrate .daily .using .fresh .solutions .

Measuring Ammonia in Solutions that Wet the MembraneThe .membrane .of .the .ammonia .electrode .is .gas-permeable .and .hydrophobic . . .Liquid .does .not .wet .the .membrane .and .liquid .does .not .penetrate .the .membrane .holes . . .If .a .sample .solution .is .nonaqueous, .or .if .it .contains .a .surfactant .that .wets .the .membrane, .the .liquid .will .penetrate .the .membrane . . .This .causes .difficulties .in .samples .such .as .sewage, .which .contains .surfactants, .and .samples .that .are .nonaqueous, .such .as .latex .paint .or .nylon . . .To .measure .ammonia .in .such .samples, .the .electrode .should .be .suspended .above .the .sample .

If .the .ammonia .electrode .is .placed .in .a .closed .system .saturated .with .water .vapor, .the .electrode .reacts .to .ammonia .in .the .gas .phase . . .Measurements .of .solutions .above .10-3 .M .ammonia . .(14 .ppm .ammonia .as .nitrogen) .are .possible .under .these .conditions .

To .measure .ammonia .in .samples .containing .surfactants, .or .nonaqueous .solutions, .adjust .the .sample .pH .to .11-13 .with .pH-adjusting .ISA . . .Transfer .the .solution .to .a .125 .mL .Erlenmeyer .flask .containing .a .magnetic .stirring .bar . . .Fit .the .neck .of .the .flask .with .a .rubber .stopper .that .has .a .hole .large .enough .to .hold .the .electrode .snugly . . .The .closed .flask .forms .an .airtight .system .whose .gas .phase .is .saturated .with .water .vapor .and .has .a .partial .pressure .of .ammonia .in .equilibrium .with .the .solution .

Normal .analytical .techniques .may .be .used .with .the .electrode .in .the .gas .phase . . .Calibrate .the .electrode .in .a .closed .flask .of .standards, .or .make .a .standard .addition .to .the .closed .flask .of .sample . . .The .electrode .in .the .gas .phase .has .a .longer .response .time .than .if .it .were .actually .in .a .surfactant-free .aqueous .solution . . .Minimum .air .space .between .solution .and .electrode .is .necessary .for .best .time .response .

�4 High Performance Ammonia Electrode User Guide

Measuring Organic NitrogenFor .information .concerning .the .measurement .of .organic .nitrogen, .contact .Technical .Support . . .Within .the .United .States .call .1 .800 .225 .1480 .and .outside .the .United .States .call .978 .232 .6000 .or .fax .978 .232 .6031 . . .In .Europe, .the .Middle .East .and .Africa, .contact .your .local .authorized .dealer . . .For .the .most .current .contact .information, .visit .www .thermo .com/water .

Nitrate Analysis Test Kit , .Cat. No. 700005

The .nitrate .analysis .test .kit .includes .one .475 .mL .bottle .each .of .alkaline .reagent .(Cat . .No . .951011), .reducing .reagent .(Cat . .No . .700006), .100 .ppm .nitrate .as .nitrogen .standard .(Cat . .No . .930707), .100 .ppm .ammonia .as .nitrogen .standard .(Cat . .No . .951207); .two .50 .mL .bottles .of .electrode .filling .solution .(Cat . .No . .951203); .and .application .procedure .number .115: .“Nitrate .Measurement .in .Environmental .Samples” .

Application NotesFor .application .notes, .such .as .measuring .ammonia .in .wastewater, .please .visit .www .thermo .com/water .and .select .the .applications .link .

��High Performance Ammonia Electrode User Guide

Known AdditionKnown .Addition .is .a .convenient .technique .for .measuring .samples .because .no .calibration .curve .is .needed . . .It .can .be .used .to .verify .the .results .of .a .direct .calibration .or .to .measure .the .total .concentration .of .an .ion .in .the .presence .of .a .large .excess .of .a .complexing .agent . . .The .sample .potential .is .measured .before .and .after .addition .of .a .standard .solution . . .Accurate .measurement .requires .that .the .following .conditions .be .met: .

• . Concentration .should .approximately .double .as .a .result .of .the .addition . .

• . Sample .concentration .should .be .known .to .within .a .factor . .of .three . .

• . In .general, .either .no .complexing .agent .or .a .large .excess .of .the .complexing .agent .must .be .present . .

• . Ratio .of .the .uncomplexed .ion .to .complexed .ion .must .not .be .changed .by .addition .of .the .standard . . .

• . All .samples .and .standards .should .be .at .the .same .temperature .

1 . . . Prepare .the .electrode .as .described .in .the .Electrode Preparation .section .

2 . . Connect .the .electrode .to .the .meter .

3 . . Prepare .a .standard .solution .that, .upon .addition .to .the .sample, .will .cause .concentration .of .the .ammonia .to .double . .Refer .to .Table 2 .as .a .guideline .

4 . . Determine .the .slope .of .the .electrode .by .performing .the .procedure .in .the .Checking Electrode Operation (Slope) section .

5 . . Rinse .the .electrode .between .solutions .by .immersing .it .in .distilled .water .and .then .blot .it .dry .

Using a Meter with a Known Addition Mode:

Note: See the meter user guide for more specific information.

1 . . . Set .the .meter .to .the .known .addition .mode .

2 . . . Measure .100 .mL .of .the .sample .into .a .beaker .

3 . . . Rinse .the .electrode .by .immersing .it .in .distilled .water, .blot .it .dry .and .then .place .it .in .the .sample .solution . . .Add .2 .mL .of . .pH-adjusting .ISA . . .Stir .the .solution .thoroughly .

4 . . . When .a .stable .reading .is .displayed, .set .the .meter .as .described .in .the .meter .user .guide, .if .required .

5 . . . Pipette .the .appropriate .amount .of .the .standard .solution .into .the .beaker . . .Stir .the .solution .thoroughly .

6 . . . When .a .stable .reading .is .displayed, .record .the .sample .concentration .

Using a Meter with a Millivolt Mode:

1 . . . . Set .the .meter .to .relative .millivolt .mode .

2 . . . . Measure .100 .mL .of .the .sample .into .a .150 .mL .beaker . . . .Add .2 .mL .of .pH-adjusting .ISA . . .Stir .the .solution .thoroughly .

3 . . . . Rinse .the .electrode .by .immersing .it .in .distilled .water, .blot .it .dry .and .then .place .it .in .the .sample .solution . . .When .a .stable .reading .is .displayed, .set .the .millivolt .reading .to .zero . . .If .the .reading .cannot .be .set .to .zero, .record .the .mV .value .

4 . . . . Pipette .the .appropriate .amount .of .standard .solution .into .the .beaker . . .Stir .the .solution .thoroughly .

5 . . . . When .a .stable .reading .is .displayed, .record .the .mV .value . . . .If .the .meter .could .not .be .zeroed .in .step .3, .subtract .the .first .reading .from .the .second .to .find .∆E .

6 . . . . From .Table 3, .find .the .Q .value .that .corresponds .to .the .change .in .potential, .∆E . . .To .determine .the .original .sample .concentration, .multiply .Q .by .the .concentration .of .the .added .standard:

Csam = QCstd

where:

. Cstd . = . standard .concentration .Csam .= . sample .concentration .Q . = . reading .from .known .addition .table

The .table .of .Q .values .is .calculated .for .a .10% .volume .change .for .electrodes .with .slope .in .the .range .of .-57 .2 .to .-60 .2 .mV . . .The .equation .for .the .calculation .of .Q .for .different .slopes .and .volume .changes .is .given .below:

(1 + p)10∆E/S - 1

where:

. Q . = . reading .from .known .addition .table

. ∆E . = . E2 .- .E1

. S . = . slope .of .the .electrode

.p . =

. volume .of .standard .

. . .volume .of .sample

Table 2

Volume of Addition Concentration of Standard

1 mL 100 x sample concentration

5 mL 20 x sample concentration

10 mL* 10 x sample concentration

* Most convenient volume to use

Table 3 Known Addition Table for an added volume one-tenth the sample volume . Slopes (in the column headings) are in units of mV/decade .

∆E Q Concentration Ratio

Monovalent (-57.2) (-58.2) (-59.2) (-60.1)

� .0 0.2894 0.2933 0.2972 0.3011� .� 0.2806 0.2844 0.2883 0.2921� .4 0.2722 0.2760 0.2798 0.2835� .� 0.2642 0.2680 0.2717 0.2754� .� 0.2567 0.2604 0.2640 0.2677

� .0 0.2495 0.2531 0.2567 0.2603� .� 0.2436 0.2462 0.2498 0.2533� .4 0.2361 0.2396 0.2431 0.2466� .� 0.2298 0.2333 0.2368 0.2402� .� 0.2239 0.2273 0.2307 0.2341

7 .0 0.2181 0.2215 0.2249 0.22827 .� 0.2127 0.2160 0.2193 0.22267 .4 0.2074 0.2107 0.2140 0.21727 .� 0.2024 02.056 0.2088 0.21207 .� 0.1975 0.2007 0.2039 0.2023

� .0 0.1929 0.1961 0.1992 0.2023� .� 0.1884 0.1915 0.1946 0.1977� .4 0.1841 0.1872 0.1902 0.1933� .� 0.1800 0.1830 0.1860 0.1890� .� 0.1760 0.1790 0.1820 0.1849

� .0 0.1722 0.1751 0.1780 0.1809 � .� 0.1685 0.1714 0.1742 0.1771� .4 0.1649 0.1677 0.1706 0.1734� .� 0.1614 0.1642 0.1671 0.1698� .� 0.1581 0.1609 0.1636 0.1664

10 .0 0.1548 0.1576 0.1603 0.163110 .� 0.1517 0.1544 0.1571 0.159810 .4 0.1487 0.1514 0.1540 0.156710 .� 0.1458 0.1484 0.1510 0.153710 .� 0.1429 0.1455 0.1481 0.1507

11 .0 0.1402 0.1427 0.1453 0.147911 .� 0.1375 0.1400 0.1426 0.145111 .4 0.1349 0.1374 0.1399 0.142411 .� 0.1324 0.1349 0.1373 0.139811 .� 0.1299 0.1324 0.1348 0.1373

1� .0 0.1276 0.1300 0.1324 0.13481� .� 0.1253 0.1277 0.1301 0.13241� .4 0.1230 0.1254 0.1278 0.13011� .� 0.1208 0.1232 0.1255 0.12781� .� 0.1187 0.1210 0.1233 0.1256

13 .0 0.1167 0.1189 0.1212 0.123513 .� 0.1146 0.1169 0.1192 0.121413 .4 0.1127 0.1149 0.1172 0.119413 .� 0.1108 0.1130 0.1152 0.117413 .� 0.1089 0.1111 0.1133 0.1155

14 .0 0.1071 0.1093 0.1114 0.113614 .� 0.1053 0.1075 0.1096 0.111814 .4 0.1036 0.1057 0.1079 0.110014 .� 0.1019 0.1040 0.1061 0.108214 .� 0.1003 0.1024 0.1045 0.1065

1� .0 0.0987 0.1008 0.1028 0.10481� .� 0.0949 0.0969 0.0989 0.10091� .0 0.0913 0.0932 0.0951 0.09711� .� 0.0878 0.0897 0.0916 0.093517 .0 0.0846 0.0865 0.0883 0.0901

��High Performance Ammonia Electrode User Guide

∆E Q Concentration Ratio

Monovalent (-57.2) (-58.2) (-59.2) (-60.1)

17 .� 0.0815 0.0833 0.0852 0.08701� .0 0.0786 0.0804 0.0822 0.08391� .� 0.0759 0.0776 0.0793 0.08101� .0 0.0733 0.0749 0.0766 0.07831� .� 0.0708 0.0724 0.0740 0.0757

�0 .0 0.0684 0.0700 0.0716 0.0732�0 .� 0.0661 0.0677 0.0693 0.0708�1 .0 0.0640 0.0655 0.0670 0.0686�1 .� 0.0619 0.0634 0.0649 0.0664�� .0 0.0599 0.0614 0.0629 0.0643

�� .� 0.0580 0.0595 0.0609 0.0624�3 .0 0.0562 0.0576 0.0590 0.0605�3 .� 0.0545 0.0559 0.0573 0.0586�4 .0 0.0528 0.0542 0.0555 0.0569�4 .� 0.0512 0.0526 0.0539 0.055

�� .0 0.0497 0.0510 0.0523 0.0536�� .� 0.0482 0.0495 0.0508 0.0521�� .0 0.0468 0.0481 0.0493 0.0506�� .� 0.0455 0.0467 0.0479 0.0491�7 .0 0.0442 0.0454 0.0466 0.0478

�7 .� 0.0429 0.0441 0.0453 0.0464�� .0 0.0417 0.0428 0.0440 0.0452�� .� 0.0405 0.0417 0.0428 0.0439�� .0 0.0394 0.0405 0.0416 0.0427�� .� 0.0383 0.0394 0.0405 0.0416

30 .0 0.0373 0.0383 0.0394 0.040531 .0 0.0353 0.0363 0.0373 0.03843� .0 0.0334 0.0344 0.0354 0.036433 .0 0.0317 0.0326 0.0336 0.034634 .0 0.0300 0.0310 0.0319 0.0328

3� .0 0.0285 0.0294 0.0303 0.03123� .0 0.0271 0.0280 0.0288 0.029737 .0 0.0257 0.0266 0.0274 0.02833� .0 0.0245 0.0253 0.0261 0.02693� .0 0.0233 0.0241 0.0249 0.0257

40 .0 0.0222 0.0229 0.0237 0.024541 .0 0.0211 0.0218 0.0226 0.02334� .0 0.0201 0.0208 0.0215 0.022343 .0 0.0192 0.0199 0.0205 0.021244 .0 0.0183 0.0189 0.0196 0.0203

4� .0 0.0174 0.0181 0.0187 0.01944� .0 0.0166 0.0172 0.0179 0.018547 .0 0.0159 0.0165 0.0171 0.01774� .0 0.0151 0.0157 0.0163 0.01694� .0 0.0145 0.0150 0.0156 0.0162

�0 .0 0.0138 0.0144 0.0149 0.0155|�1 .0 0.0132 0.0137 0.0143 0.0148�� .0 0.0126 0.0131 0.0136 0.0142�3 .0 0.0120 0.0125 0.0131 0.0136�4 .0 0.0115 0.0120 0.0125 0.0130

�� .0 0.0110 0.0115 0.0120 0.0124�� .0 0.0105 0.0110 0.0115 0.0119�7 .0 0.0101 0.0105 0.0110 0.0114�� .0 0.0096 0.0101 0.0105 0.0109�� .0 0.0092 0.0096 0.0101 0.0105�0 .0 0.0088 0.0092 0.0096 0.0101

Electrode Characteristics

Electrode ResponseThe .electrode .exhibits .good .time .response .(one .minute .or .less) .for .ammonia .concentrations .above .1 .ppm .ammonia .as .nitrogen . . .Below .this .value, .response .times .are .longer .and .ammonia .absorption .from .the .air .may .become .a .source .of .error . . .Above .1 .0 .M, .ammonia .is .rapidly .lost .to .the .air . . .Samples .above .1 .0 .M .ammonia .concentration .can .be .diluted .before .measurement . . .

For .solutions .with .low .concentration .in .ammonia .but .high .in .total .ionic .strength, .perform .the .same .procedure .with .one .change: . .prepare .a .calibration .solution .with .a .background .composition .similar .to .the .sample . . .Accurate .measurement .requires .that .the .following .conditions .be .met .

• . Adequate .time .must .be .allowed .for .electrode .stabilization . .Longer .response .time .will .be .needed .for .low-level .measurements .

• . Remember .to .stir .all .standards .and .samples .at .a .moderate, .uniform .rate . .When .plotted .on .semi-logarithmic .paper, .electrode .potential .response .as .a .function .of .ammonia .concentration .is .a .straight .line .with .a .slope .of .about .-58 .mV .per .decade .

Figure 20: Typical Electrode Response To Step Changes in Ammonia Concentration

10 to 0.01 ppm NH3 as N

10 to 0.1 ppm NH3 as N

10 to 1 ppm NH3 as N

10 ppm NH3 as N

10 to 100 ppm NH3 as N

50 100 150 200 250 300

time (sec)

Temperature EffectsA .change .in .temperature .will .cause .electrode .response .to .shift .and .change .slope . . .Table 4 .lists .the .variation .of .theoretical .response .with .temperature . . .At .10-3 .M, .a .1 .˚C .temperature .change .gives .rise .to .a .2% .error . . .Samples .and .standards .should .be .at .the .same .temperature . . .Note .that .the .higher .the .temperature, .the .faster .the .ammonia .loss .from .solution .

Table 4

Temperature (˚C) Slope (mV)

0 -54 .20

5 . . . -55 .20

10 . . -56 .18

15 . . -57 .17

20 . . -58 .16

25 . . -59 .16

30 . . -60 .15

35 . . -61 .14

40 . . -62 .13

InterferencesVolatile .amines .interfere .with .electrode .measurements . . .Most .gases .do .not .interfere .as .they .are .converted .to .the .ionic .form .in .basic .solution . . .Ionic .species .cannot .cross .the .gas-permeable .membrane .and .are .not .direct .electrode .interferences . . .However, .the .level .of .ions .in .solution .can .change .the .solubility .of .ammonia . . .Standards .and .samples .should .have .about .the .same .level .of .ions .in .the .solution .and .about .the .same .level .of .dissolved .species . . .Also, .some .metallic .ions .complex .ammonia, .causing .falsely .low .results .in .direct .measurements . . .The .pH-adjusting .ISA, .Cat . .No . .951211, .removes .interferences .from .metallic .ions .

pH EffectsThe .pH .of .all .standards .and .samples .must .be .adjusted .above .11 .before .they .can .be .measured . . .

ComplexationAmmonia .forms .metal .complexes .with .a .number .of .metal .ions: . .mercury, .silver, .copper, .gold, .nickel, .cobalt, .cadmium, .and .zinc . . .Most .of .these .metals .are .removed .in .the .form .of .hydroxide .complexes .or .precipitates .in .basic .solution . . .When .hydroxide .is .present .at .the .0 .1 .M .level .and .the .ammonia .concentration .is .below .10-3 .M, .only .mercury .will .appreciably .complex .ammonia . . .The .total .ammonia .level .of .the .sample .will .be .measured .if .the .mercury .in .the .sample .is .preferentially .bound .to .some .other .species . . .Iodide .is .recommended .for .this .purpose, .since .it .forms .a .soluble .mercury .complex .at .all .pH .levels . . .Use .of .pH-adjusting .ISA .inhibits .the .formation .of .some .these .common .metal .complexes .in .the .sample, .because .it .contains .a .high .concentration .of .hydroxide .ion .and .a .reagent .that .removes .mercury .and .silver .ions .

Effect of Dissolved SpeciesWater .vapor .is .a .potential .electrode .interference . . .Water .can .move .across .the .membrane .as .water .vapor, .changing .the .concentration .of .the .electrode .filling .solution .under .the .membrane . . .Such .changes .will .be .seen .as .electrode .drift . . .Water .vapor .transport .across .the .membrane .is .not .a .problem .if .the .total .level .of .dissolved .species .in .solution .(osmotic .strength) .is .below .1 .M . .or .the .electrode .and .sample .temperatures .are .the .same . . .Addition .of .ISA .to .samples .of .low .osmotic .strength .automatically .adjusts .them .to .the .correct .level . . .Samples .with .osmotic .strengths .above .1 .M .should .be .diluted .before .measurement . . .Dilution .should .not .reduce .the .ammonia .level .below .10-5 .M . . .Samples .with .high .osmotic .strengths .(above .1 .M) .and .low .ammonium .levels .(below .10-5 .M) .can .be .measured .without .dilution .if .the .osmotic .strength .of .the .electrode .filling .solution .is .adjusted . . .To .adjust .the .electrode .filling .solution, .add .4 .25 .g .solid .NaNO3 .to .each .100 .mL .electrode .filling .solution .

Membrane LifeA .membrane .will .last .from .one .week .to .several .months, .depending .on .usage . . .Membrane .failure .is .characterized .by .a .shift .in .electrode .potential, .drift .or .poor .response . . .Refer .to .Troubleshooting .section . . . .

Theory of OperationThe .ammonia .electrode .uses .a .hydrophobic .gas-permeable .membrane .to .separate .the .sample .solution .from .the .electrode .filling .solution . . .Dissolved .ammonia .in .the .sample .solution .diffuses .through .the .membrane .until .the .partial .pressure .of .ammonia .is .the .same .on .both .sides .of .the .membrane . . .In .any .given .sample .the .partial .pressure .of .ammonia .will .be .proportional .to .its .concentration .

Ammonia .diffusing .through .the .membrane .dissolves .in .the .filling .solution .and, .to .a .small .extent, .reacts .reversibly .with .water .in .the .filling .solution .

NH3 + H2O NH4+ +OH-

The .relationship .between .ammonia, .ammonium .ion .and .hydroxide .is .given .by .the .following .equation:

. [NH4] [OH-] = constant

The .electrode .filling .solution .contains .ammonium .chloride .at .a .sufficiently .high .level .so .that .the .ammonium .ion .concentration .can .be .considered .fixed . .Thus:

[OH-] = [NH3] • constant

The .potential .of .the .electrode .sensing .element .with .respect .to .the .internal .reference .element .is .described .by .the .Nernst .equation:

E = E0 - S log [OH-]

where:

E = . measured .electrode .potential E0 = . reference .potential OH- = . .hydroxide .concentration .in .solution S = . electrode .slope .(-59 .2 .mV/decade)

Since .the .hydroxide .concentration .is .proportional .to .ammonia .concentration, .electrode .response .to .ammonia .is .also .Nernstian .

E = E0 - S log [NH3]

The .reference .potential, .E0, .is .partly .determined .by .the .internal .reference .element .that .responds .to .the .fixed .level .of .chloride .in .the .filling .solution .

Ammonium IonWhen .ammonia .is .dissolved .in .water .it .reacts .with .hydrogen .ion .to .form .ammonium .ion:

NH3 + H3O+ NH4+ + H2O

The .relative .amount .of .ammonia .and .ammonium .ion .is .determined .by .the .solution .pH .(see .Figure 21) . . .In .acid .solution, .where .hydrogen .ion .is .readily .available, .virtually .all .the .ammonia .is .converted .to .ammonium .ion . . .At .a .pH .of .about .9 .3, .half .the .ammonia .will .be .in .the .form .of .ammonium .ion .

Theoretically, .it .is .possible .to .calculate .the .ratio .of .ammonia .to .ammonium .ion, .if .the .pH .is .known . . .The .equilibrium .constant .for .the .reaction .is:

. . . . . .[NH4+]

= [NH4

+] = K 10-9.3

[H3O+][NH3] 10-pH [NH3]

at .25 .˚C .µ= .0 .1 .and .pK .= .9 .3 . . .

The .ratio .of .ammonium .to .ammonia .is .given .by:

[NH4+]

= K 10-pH = 109.3-pH

Martell, .A .; .Smith, .R ., .Critical .Stability .Constants, .Plenum .Press . . .New .York, .NY, .1974 .

The .exact .value .of .K .will .vary .with .both .temperature .and .ionic .strength . . .For .example, .while .the .pK, .at .25 .˚C .and .µ .= .0 .1, .is .given .as .9 .3 .(as .in .the .discussion .above) .an .increase .in .ionic .strength .to .µ .= .1 .0 .yields .a .pK .of .9 .4 .

Partial Pressure of AmmoniaAs .discussed .in .the .Theory of Operation .section, .the .ammonia .electrode .responds .to .the .partial .pressure .of .dissolved .ammonia .gas . . .The .partial .pressure .of .dissolved .ammonia .gas .is .related .to .the .ammonia .concentration .by .Henry’s .Law:

Kh = [NH3] aqueous

= 56 moles/liter - atm. (25 ˚C) PNH3

The .Henry’s .Law .constant, .Kh, .varies .both .with .temperature .and .the .level .of .dissolved .species . . .For .example, .the .constant .is .about .20% .lower .in .1 .M .NaCl .that .in .distilled .water .

To .keep .the .Henry’s .Law .constant .close .to .the .same .value, .standards .and .samples .should .contain .the .same .level .of .dissolved .species .and .be .about .the .same .temperature .

Figure 21: Percent of Ammonia and Ammonium as a Function of pH

6 7 8 9 10 11 12 13 14

ammonia

ammonium

solution pH

% ofspecies

Troubleshooting

Troubleshooting Checklist

Symptom: Off-scale or over-range reading

Membrane .failure– . .Replace .the .membrane . .Refer .to .the .Electrode Preparation .section .for .instructions .

Inner .body .not .properly .conditioned– . .Soak .the .inner .body .in .electrode .filling .solution .for .at .least .two .hours . .For .best .results, .soak .the .inner .body .overnight .

Inner .body .defective– . .Refer .to .the .Troubleshooting Guide .section .and .perform .the .checking .inner .body .procedure .

Electrode .filling .solution .not .added– . .Fill .the .electrode .up .to .the .fill .line .with .electrode .filling .solution .

Air .bubble .on .the .membrane– . .Remove .bubbles .by .gently .tapping .the .side .of .the .electrode .

Electrode .not .in .solution– . .Insert .the .electrode .in .solution .

Electrode .not .plugged .into .the .meter .properly– . .Unplug .and .reconnect .the .electrode .

Defective .meter– . .Perform .the .meter .checkout .procedure .(refer .to .the .meter .user .guide) .

Symptom: Low slope or no slope

Standards .contaminated .or .made .incorrectly– . .Prepare .fresh .standards .

ISA .not .used .or .incorrect .ISA .used– . .Use .pH-adjusting .ISA, .Cat . .No . .951211, .when .working .with .ammonia .samples .that .have .concentrations .of .1 .ppm .ammonia .as .nitrogen .or .higher . .Add .2 .mL .of .pH-adjusting .ISA .to .every .100 .mL .of .standard .and .sample . . .Use .alkaline .reagent .(low-level .ISA), .Cat . .No . .951011, .when .working .with .ammonia .samples .that .have .concentrations .of .1 .ppm .ammonia .as .nitrogen .or .lower . .Add .1 .mL .of .alkaline .reagent .to .every .100 .mL .of .standard .and .sample .

Electrode .exposed .to .air .for .extended .period– . .Replace .the .membrane . .Refer .to .the .Electrode Preparation .section .for .instructions .

Symptom: Noisy or unstable readings (erratic, rapidly changing)

Insufficient .electrode .filling .solution– . .Fill .the .electrode .up .to .the .fill .line .with .electrode .filling .solution .

Membrane .cap .loose– . .Ensure .that .the .membrane .cap .is .screwed .on .tight .enough .to .close .the .gap .between .the .cap .and .body .

ISA .not .used– . .Use .the .recommended .ISA .

Defective .meter– . .Perform .the .meter .checkout .procedure .(refer .to .the .meter .user .guide) .

Symptom: Wrong answer but calibration curve is correct

Standards .contaminated .or .made .incorrectly– . .Prepare .fresh .standards .

Incorrect .scaling .of .semi-logarithmic .paper– . .Refer .to .the .Direct Calibration .section .

Incorrect .millivolt .sign .used– . .Make .sure .to .correctly .record .the .sign .of .mV .values .

Incorrect .units .used– . .Apply .the .correct .conversion .factor: . .10-3 .M . .= . .17 .ppm .as .NH3 . .= . .14 .ppm .as .N

Complexing .agents .in .sample– . .Use .known .addition, .titration .techniques .or .a .decomplexing .procedure .

ISA .added .to .standards, .but .not .samples– . .Add .the .same .proportion .of .ISA .to .all .standards .and .samples .

Both .ISA .solutions .used .for .one .analysis– . .To .keep .the .dilution .ratio .the .same, .use .only .one .type .of .ISA .for .each .calibration .and .measurement .set . . .Use .pH-adjusting .ISA, .Cat . .No . .951211, .with .ammonia .samples .that .are .1 .ppm .and .higher . . .Use .alkaline .reagent .(low-level .ISA), .Cat . .No . .951011, .with .ammonia .samples .that .are .1 .ppm .and .lower . . .

Symptom: Drift (reading slowly changing in one direction) .

Ammonia .loss .from .sample .sitting .too .long– . .Reduce .the .surface .area .to .volume .ratio, .slow .the .rate .of .stirring .and .avoid .high .temperatures .

Filling .solution .leaking– . .Ensure .that .the .membrane .is .installed .properly . .Refer .to .the .Electrode Preparation .section .

Electrode .not .assembled .properly– . .Ensure .that .the .inner .body .is .fully .inserted .in .the .top .of .the .outer .body .when .assembling .the .electrode . .Refer .to .the .Electrode Preparation .section . .

Samples .and .standards .at .different .temperatures– . .Allow .solutions .to .come .to .room .temperature .before .measurement .

Incorrect .electrode .filling .solution .used– . .Fill .the .electrode .using .the .correct .electrode .filling .solution, .Cat . .No . .951209 .

Total .level .of .dissolved .species .above .1 .M– . .Dilute .solutions .

Meter .or .stirrer .improperly .grounded– . .Check .meter .and .stirrer .for .grounding .issues .

Solutions .not .at .constant .temperature– . .Allow .solutions .to .come .to .room .temperature .before .use .

Magnetic .stirrer .generating .heat– . .Place .insulating .material .between .the .magnetic .stirrer .and .beaker .

Electrode .exposed .to .air .for .extended .period– . .Replace .the .membrane . .Refer .to .the .Electrode Preparation .section .for .instructions .

Troubleshooting GuideThe .most .important .principle .in .troubleshooting .is .to .isolate .the .components .of .the .system .and .check .each .in .turn . . .The .components .of .the .system .are .the .meter, .electrode, .standard, .sample .and .technique .

The .meter .is .the .easiest .component .to .eliminate .as .a .possible .cause .of .error . . .Thermo .Scientific .Orion .meters .include .an .instrument .checkout .procedure .in .the .meter .user .guide .and .a .shorting .strap .for .convenience .in .troubleshooting . . .Consult .the .user .guide .for .complete .instructions .and .verify .that .the .instrument .operates .as .indicated .and .is .stable .in .all .steps .

Electrode

1 . . Rinse .the .electrode .thoroughly .with .distilled .water .

2 . . . Perform .Checking Electrode Operation (Slope) .procedure .

3 . . . If .the .electrode .fails .this .procedure, .replace .the .membrane .and .soak .the .electrode .as .directed .in .the .Electrode Preparation section .

4 . . . Repeat .the .Checking Electrode Operation (Slope) .procedure .

5 . . . If .the .electrode .still .does .not .perform .correctly, .perform .the .Checking Inner Body .procedure .to .determine .if .the .inner .body .is .working .properly .

Checking Inner Body:

Solution 1– .pH .4 .01 .buffer .with .0 .1 .M .NH4Cl .or .0 .1 .M .NaCl

. .Take .100 .mL .of .pH .4 .01 .buffer, .Cat . .No . .910104, .and .add .0 .54 .g .of .reagent-grade .NH4Cl .or .0 .58 .g .of .reagent-grade .NaCl . . .Thoroughly .stir .the .solution .and .label .the .bottle .as .Solution .1 . . .Store .the .buffer .for .repeated .use . . .Discard .the .buffer .if .turbidity .develops . .

Solution 2– .pH .7 .00 .Buffer .with .0 .1 .M .NH4Cl .or .0 .1 .M .NaCl .

. .Take .100 .mL .of .pH .7 .00 .buffer, .Cat . .No . .910107, .and .add .0 .54 .g .of .reagent-grade .NH4Cl .or .0 .58 .g .of .reagent-grade .NaCl . . .Thoroughly .stir .the .solution .and .label .the .bottle .as .Solution .2 . . .Store .the .buffer .for .repeated .use . . .Discard .the .buffer .if .turbidity .develops .

Note: The temperature of the buffers and distilled water must be 25 °C ± 4 °C and all solutions should be at same temperature within ± 1° C.

. Disassemble .the .ammonia .electrode . . .If .the .electrode .is .dry, .soak .the .glass .tip .of .the .inner .body .in .filling .solution .for .at .least .two .hours . . .Rinse .the .inner .body .with .distilled .water .and .immerse .it .in .pH .7 .buffer .with .0 .1 .M .NH4Cl .added . . .Make .sure .that .the .coiled .reference .wire .is .completely .covered . . .Stir .the .solution .throughout .the .procedure . . .Record .the .millivolt .reading .after .two .minutes .

Rinse .the .inner .body .in .distilled .water .and .place .in .the .pH .4 .buffer .with .0 .1 .M .NH4Cl .added . . .Watch .the .change .in .meter .reading .carefully . . .The .reading .should .change .by .100 .mV .in .less .than .30 .seconds .after .immersion .in .the .pH .4 .buffer . . .After .three .minutes .the .mV .difference .between .pH .7 .and .pH .4 .should .be .greater .than .150 .mV .if .the .inner .body .is .operating .correctly .

6 . . If .the .stability .and .slope .check .out .properly, .but .measurement .problems .still .persist, .the .sample .may .contain .interferences .or .complexing .agents, .or .the .technique .may .be .in .error . . .Refer .to .the .Standard, .Sample, .and .Technique .sections .

7 . . Before .replacing .a .“faulty” .electrode, .review .the .instruction .manual .and .be .sure .to:

. • . . .Clean .the .electrode .thoroughly

. • . . .Prepare .the .electrode .properly

. • . . . .Use .proper .electrode .filling .solution, .ISA .and .standards

. • . .Review .the .Troubleshooting Checklist section

Standard

The .quality .of .results .depends .greatly .upon .the .quality .of .the .standards . . .Always .prepare .fresh .standards .when .problems .arise, .it .could .save .hours .of .frustrating .troubleshooting . . .Errors .may .result .from .contamination .of .prepared .standards, .accuracy .of .dilution, .quality .of .distilled .water, .or .a .mathematical .error .in .calculating .the .concentrations . . .The .best .method .for .preparation .of .standards .is .by .serial .dilution . . .Refer .to .the .Direct Calibration section .

Sample

If .the .electrode .works .properly .in .standards .but .not .in .the .sample, .look .for .possible .interferences, .complexing .agents .or .substances .that .could .alter .the .electrode .response .or .physically .damage .the .electrode . . .If .possible, .determine .the .composition .of .the .samples .and .check .for .problems . . .Refer .to .the .Sample Requirements, .Interferences, .and .pH Requirements .sections .

Technique

Check .the .method .of .analysis .for .compatibility .with .your .sample . . .Direct .measurement .may .not .always .be .the .method .of .choice . . .If .large .amounts .of .complexing .agents .are .present, .known .addition .may .be .best .method . . .If .the .sample .is .viscous, .analate .addition .may .solve .the .problem . . .If .working .at .low .levels, .be .sure .to .follow .the .low-level .measurement .technique . . .Also, .be .sure .that .the .expected .concentration .of .the .ion .of .interest .is .within .the .electrode’s .limit .of .detection . .If .problems .persist, .review .operational .procedures .and .instruction .manuals .to .be .sure .that .proper .technique .has .been .followed . . .Refer .to .the .Measuring Hints .and .Analytical Techniques sections .

Assistance After .troubleshooting .all .components .of .your .measurement .system, .contact .Technical .Support . . .Within .the .United .States .call .1 .800 .225 .1480 .and .outside .the .United .States .call .978 .232 .6000 .or .fax .978 .232 .6031 . . .In .Europe, .the .Middle .East .and .Africa, .contact .your .local .authorized .dealer . . .For .the .most .current .contact .information, .visit .www .thermo .com/water .

WarrantyFor .the .most .current .warranty .information, . .visit .www .thermo .com/water .

Ordering Information

9512HPBNWP High .performance .ammonia .electrode .with .waterproof .BNC .connector

9512HP01 High .performance .ammonia .electrode .with .U .S . .standard .connector

951214* Loose .membranes, .box .of .20

951215* Preassembled .outer .body .and .membrane .cap .assembly, .3 .pack

951211 pH-adjusting .ISA, .475 .mL .bottle

951011 Alkaline .reagent .(low-level .ISA), .475 .mL .bottle

951209 Electrode .filling .solution, .60 .mL .bottle

951006 0 .1 .M .NH4Cl .standard, .475 .mL .bottle

951007 1000 .ppm .ammonia .as .nitrogen .standard, .475 .mL .bottle

951207 100 .ppm .ammonia .as .nitrogen .standard, .475 .mL .bottle

* . . .Use .with .the .9512HPBNWP .and .9512HP01 .high .performance .ammonia .electrodes .only

Specifications

Concentration Range5 .x .10-7 .to .1 .M .0 .01 .to .17,000 .ppm .as .ammonia .(NH3) .0 .01 .to .14,000 .ppm .as .nitrogen .(N)

pH RangeSamples .and .standards .must .be .adjusted .above .pH .11

Temperature Range0 .to .50 .°C

Electrode ResistanceLess .than .1,500 .megohms

Slope-54 .to .-60 .mV . .(in .the .linear .range .of .the .electrode, .with .all .solutions .at .25 .°C .± .4 .°C .and .with .all .solutions .at .same .temperature .within .± .1° .C)

Response Time1 .minute .or .less .(at .higher .concentrations .and .with .ideal .electrode .conditions)

SizeElectrode .Length: . .115 .mm

Body .Diameter: .12 .mm

Cap .Diameter: .16 .mm

Cable .Length: . .1 .meter

Note: Specifications subject to change without notice

Thermo Fisher Scientific

Environmental Instruments DivisionWater Analysis Instruments

166 Cummings CenterBeverly, MA 01915 USATel: 978-232-6000Toll Free: 800-225-1480Dom. Fax: 978-232-6015Int’l. Fax: 978-232-6031

www.thermo.com/water253363-001 Rev.A

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